Saw this last week when a customer brought in a flat to be repaired. The tire was a standard 2" MTB tire, and the tube was a 1.25-1.75" thorn resistant heavyweight, with a presta valve. The tube had stretched to fill the tire, but there was a puncture at the base of the valve stem. The heavier, less flexible rubber at the base of the valve stem had not stretched with the rest of the tube it split.
In a pinch I might stretch an 18-23c tube to fill a 25c tire, but any greater difference is probably asking too much of a butyl tube.